System and method for the dynamic display of three-dimensional image data

ABSTRACT

The present invention provides a system for the dynamic display of three-dimensional (3D) images of a target, comprising: memory means to store the plurality of time-dependent 3D image data sets; an address pointer defining an independent address of a location in the memory means of each time-dependent 3D image data set; and display means utilizing the address pointer successively to retrieve a time-dependent 3D image data set from memory and display a time-dependent 3D image corresponding to the time-dependent 3D image data set for a selected period of time. A method for dynamic display of 3D images is also provided.

This application claims the benefit of provisional application No.60/050,779, filed Jun. 25, 1999.

TECHNICAL FIELD

The present invention relates to the field of image data display. Morespecifically, the present invention relates to a system and method forthe dynamic display of three-dimensional image data.

BACKGROUND ART

Three-dimensional (3D) ultrasound imaging is a technique in which a setof spatially related two dimensional ultrasound slices (tomograms) of atarget are collected and mathematically converted to create a virtualCartesian ultrasound volume. This virtual ultrasound volume facilitatesthe visualization of non-acquired slices of the target and a variety ofrendered surfaces and projections of the target otherwise unobtainableusing two-dimensional (2D) ultrasound imaging.

High fidelity 3D ultrasound requires, by definition, a data set in whichthe spacial relationship between the individual ultrasound slices isprecisely known. High fidelity ultrasound is important for the accurateassessment of volumes and the appreciation of target geometry. Theconventional method of choice for obtaining the precise spatialrelationship between ultrasound slices is to actively constrain theposition of each ultrasound slice. This is achieved by controlling theposition of the ultrasound probe during generation of the slices by useof a motorized positioning device (mechanical scanning). Examples of 3Dultrasound imaging systems are described in detail in U.S. Pat. No.5,454,371 (Fenster et al.) and U.S. Pat. No. 5,562,095 (Downey et al.),the contents of each of which are hereby incorporated by reference.

In the three-dimensional ultrasound imaging systems described in theafore-mentioned United States patents, when a succession oftwo-dimensional images have been captured and digitized, thetwo-dimensional images are stored as a stack to form an image dataarray. Before a three-dimensional image of the scanned volume can becreated and viewed by a user, the image data array must be reconstructedto form a volumetric image array. This type of reconstruction, in whichevery pixel in every two-dimensional image slice is converted into anappropriate voxel in an image volume (i.e. volumetric image array) priorto display is known as “full volume” reconstruction. The generation ofthe complete volume array is somewhat inefficient, i.e. it is atime-consuming intermediate stage. Full volume reconstruction anddisplay of a three-dimensional image using a conventional hardwareplatform can take upward of one minute and, therefore, has limitedapplication in situations where immediate display of an acquired imageis desirable.

In an attempt to overcome the drawbacks associated with full volumereconstruction, the applicants developed a so-called “fast”reconstruction process which is described in copending U.S. patentapplication Ser. No. 08/562,590 (which corresponds to Internationalpatent application publication number WO 97/20288), and U.S. provisionalpatent application serial No. 60/041,345, filed Mar. 21, 1997, thecontents of each of which are hereby incorporated by reference.

In fast reconstruction, only the specific image data from thetwo-dimensional image slices that are actually required to view theuser-selected image undergoes reconstruction. In other words, only theimage data necessary to view the surface of user-selected image (i.e. asopposed to all of the data representing the entire volume of the target)is used for reconstruction. If, for example, the users wishes to view aparticular image of the target volume, the computer uses associatedcalibration and acquisition parameters of the collected two-dimensionalimage slices to determine special “look-up” tables which speed up thedetermination of which data points from the two-dimensional image slicesare required to be displayed on the monitor. Only the two-dimensionaldata points necessary to produce the desired image are reconstructed.There is no necessity to construct a full volume image array.Accordingly, this fast reconstruction is more efficient thanconventional full volume reconstruction, i.e. it is less time-consuming(less than {fraction (1/2+L )} second).

Both “full volume” and “fast” reconstruction techniques are capable ofgenerating and displaying high quality, single, three-dimensional imagesof a target, i.e., a temporal “snap-shot” of the target. Thesetechniques are particularly useful in displaying images of non-dynamic,effectively stationary targets such as the breast, prostate or liver.However, the display of a single “snap-shot” is not optimally effectivefor imaging a dynamic target such as the heart or lungs.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a system and methodfor dynamic image display which obviates and mitigates at least one ofthe disadvantages of the prior art.

Accordingly, in one aspect the present invention provides a system forthe dynamic display of three-dimensional (3D) images of a target,comprising:

memory means to store a plurality of time-dependent 3D image data sets;

an address pointer defining an independent address of a location in thememory means of each time-dependent 3D image data set; and

display means utilizing the address pointer successively to retrieve atime-dependent 3D image data set from memory and display atime-dependent 3D image corresponding to the time-dependent 3D imagedata set for a selected period of time.

In another of its aspects, the present invention provides a system forthe dynamic display of three-dimensional (3D) images of a target volume,the system comprising:

scanning means to scan a target volume and generate a succession ofdigitized two-dimensional (2D) images thereof;

timing means to determine the time interval between generation of thesuccession of 2D images;

reconstruction means to generate a plurality of time-dependent 3D imagedata sets of the target volume from the succession of digitized 2Dimage;

memory means to store the plurality of time-dependent 3D image datasets;

an address pointer defining an independent address of a location in thememory means of each time-dependent 3D image data set; and

display means utilizing the address pointer successively to retrieve atime-dependent 3D image data set from memory and display atime-dependent 3D image corresponding to the time-dependent 3D imagedata set for a selected period of time.

In yet another of its aspects, the present invention provides a methodfor the dynamic display of three-dimensional (3D) images of a target,comprising the steps:

(i) storing a plurality of time-dependent 3D image data sets in amemory;

(ii) defining an independent address of a location in the memory meansfor each time-dependent 3D image data set; and

(iii) retrieving a time-dependent 3D image data set from memory;

(iv) displaying the time-dependent 3D image corresponding to thetime-dependent 3D image data set for a selected period of time; and

(v) repeating Steps (iii) and (iv) for each remaining time-dependent 3Dimage data set.

In yet another of its aspects, the present invention provides a methodfor the dynamic display of three-dimensional (3D) images of a targetvolume, the system comprising:

(i) scanning a target volume and generating a succession of digitizedtwo-dimensional (2D) images thereof;

(ii) determining the time interval between generation of the successionof 2D images;

(ii) generating a plurality of time-dependent 3D image data sets of thetarget volume from the succession of digitized 2D image;

(iii) storing a plurality of time-dependent 3D image data sets in amemory;

(iv) defining an independent address of a location in the memory meansfor each time-dependent 3D image data set; and

(v) retrieving a time-dependent 3D image data set from memory;

(vi) displaying the time-dependent 3D image corresponding to thetime-dependent 3D image data set for a selected period of time; and

(vii) repeating Steps (v) and (vi) for each remaining time-dependent 3Dimage data set.

The terms “dynamic image display” and “dynamic display ofthree-dimensional images” are used interchangeably throughout thisspecification and are intended to include any method and/or systemcapable of displaying, in a time-dependent sequential manner, a threedimensional image of a target (e.g., organ, bodily structure, etc.)which is in a state of motion. The effect of this is to enable threedimensional visualization of changes in a target over time. Non-limitingexamples of applications of dynamic image display in which the presentinvention is useful include imaging of a beating heart, assessment thechange of a physiological structure in the process of diseaseprogression and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described, by way ofexample only, with reference to the following figures, in which:

FIG. 1 is a schematic representation of the dynamic imaging methodaccording to one embodiment of the present invention; and

FIGS. 2a-2 k illustrate time-dependent, sequential three-dimensionalphotographic images of a beating heart obtained using the present methodand system.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 illustrates the schematic for a system 10 for the dynamic displayof three-dimensional (3D) images of a target. System 10 generallycomprises a memory 20 to store a plurality of time-dependent 3D imagedata sets 30 a-30 e and at least one address pointer defining anindependent address of a location in memory 20 of each of time-dependent3D image data set 30 a-30 e. Of course those of skill in the art willrecognize that the precise number of time-dependant 3D image data setsis not particularly restricted.

In the illustrated embodiment, the concordance between respectivetime-dependent 3D image data sets and addresses in memory 20 is asfollows:

3D Image Data Set Address in Memory 20 30a 35 30b 40 30c 41 30d 42 30e43

As illustrated, the individual 3D image data sets are preferably ofsubstantially the same size and parameter.

System 10 further comprises a display means 50 which utilizes theaddress pointer to retrieve a first time-dependent 3D image data set 30a from address 35 in memory 20 and display the first time-dependent 3Dimage (30 a′) for a selected period of time defined by timer 60.

After the selected period of time, display means 50 retrieves another inthe succession of time-dependent 3D image data sets 30 b-30 e fromaddresses 40-43, respectively, in memory 20 using the address pointer,and displays this second time-dependent 3D image, in place of the firsttime-dependent 3D image, for a selected period of time defined by timer60.

As will be apparent, the duration of display of each of the successivetime-dependent 3D images is not particularly limited and not all theimages in a particular series need be displayed for the same length oftime. Further, the number of time-dependent 3D image data sets in aseries is not limited. The example in shown in FIG. 1 has a series offive time-dependent 3D image data sets. However, for the purposes of thepresent invention, only two different time-dependent 3D image data setsare required. Generally, there are three factors which should be takeninto account in application of the present method and system: (i) theprocessor speed of the computer used to conduct image reconstruction;(ii) the duration of the total time interval over which the 3D imagedata sets are acquired; and (iii) the number of image data sets selectedby the user. Thus, if the target is a beating heart and the goal is toimage a single heartbeat (total time interval of approximately 1-2seconds), given current computer processors, the number of 3D image datasets generally will be less than 20 and possibly less than 10.Alternatively, if the target is a muscle and the goal is to image it inflexure (total time interval of approximately 5 seconds), given currentcomputer processors, the number of 3D image data sets generally will beless than about 50 and possible less than 20.

The system of the present invention is particularly useful in the fieldof medical imaging, where it can be used to display dynamic 3D images ofmoving tissue. The inventors have successfully used the system andmethod of this invention to produce real-time, dynamic 3Dultrasonographic images of the human heart, as will be described below.

A Hewlett-Packard HP Sonos 2500™ ECO cardiology ultrasound machine, theoperation manual of which is hereby incorporated by reference, was usedin standard configuration to acquire a plurality of two-dimensional (2D)ultrasound images of a beating heart. The data was acquired using anaxial scanning technique with a clockwise sweep of 180°. The dataacquisition time was six minutes and the data was split into twenty twosuccessive phases of the heart beat. For ease of data management, 3Dimages of only eleven of these successive phases were constructed. Each3D image comprised 91 2D frames of 224×216 pixels. This type of cardiacdata acquisition and 3D image reconstruction are both well known in theart and are described in more detail in the above-mentioned U.S. Pat.No. 5,454,371 (Fenster et al.) and U.S. Pat. No. 5,562,095 (Downey etal.).

The eleven successive 3D images generated are shown in FIGS. 2a- 2 k.FIGS. 2a-2 f show the systolic phase of the heart beat, while FIGS. 2g-2k show the diastolic phase of the heart beat.

Each of the time-dependent 3D image data sets used to generate images 2a-2 k are stored in a computer memory in series to give afour-dimensional (4D) data set, where time is the fourth dimension. Anaddress pointer defines the location within the memory of the 4D dataset and the location within the memory of the start of each of theindividual 3D image data sets in the 4D data set. Each image can beretrieved from memory and displayed successively for a period of timedetermined by the user. Further, knowing the heart-rate of the subject,the entire series of 3D images can be displayed in succession in acontinuous loop to give a real-time image of the beating heart.

The present invention is not limited to the display of ultrasoundimages. For example, it is envisioned that this dynamic displaytechnique may also be useful in the display of magnetic resonance orcomputed X-ray tomographic data. Further, it is envisioned that the 4Ddata set may not necessarily solely contain time-dependent 3D image dataacquired using a single technique. For example, it may be desirable toshow successive images of a target where each image is acquired using adifferent technique (i.e., combining magnetic resonance, computed X-raytomographic and ultrasound images in a single 4D data set).

Preferably, the present method and system are directed toward ultrasonic3D imaging. When the present method and system are used in conjunctionwith ultrasonic 3D imaging it is preferred to incorporate the “fast”reconstruction technique described in copending U.S. patent applicationSer. No. 08/562,590 (which corresponds to International patentapplication publication number WO 97/20288), and U.S. provisional patentapplication Ser. No. 60/041,345, filed Mar. 21, 1997, the contents ofeach of which are hereby incorporated by reference.

When the “fast” reconstruction technique is used with the present methodand system, it is preferred to design the address pointer such that itis sequentially incremented to allow it to switch between the modalitydescribed hereinabove with reference to Figure and the modality in the“fast” reconstruction technique as described in the copendingapplications incorporated herein by reference. The effect of this asfollows. The “fast” reconstruction technique, as described in thecopending applications incorporated herein by reference, allowsmanipulation of the displayed image via graphical input device (e.g., amouse) to allow manipulations, with a single 3D image data set, such asrotation of the entire displayed 3D image about an arbitrary axis,translation of a selected plane of the displayed 3D image and rotationof a selected plane of the displayed 3D image about an arbitrary axis.In the context of the present method and system, the address pointer maybe used to identify in a particular 3D image data set the addresscorresponding to a desired manipulation. Once this is done, the addresspointer can be used as described hereinabove with reference to FIG. 1 to“refresh” the display image corresponding to the remaining 3D image datasets (recall it is preferred that the various 3D image data sets be ofsubstantially the same size and parameter). The practical result of thisis that the user simply manipulates one frame of the displayed image(i.e., reconstructed from one 3D image data set) and the remainingframes are displayed with a corresponding manipulation (i.e.,reconstructed from each of the remaining 3D image data sets). The actualchoice and design of an address pointer to switch between two modalitiesas described above is within the purview of a person skilled in the art.

While this invention has ben described with reference to an illustrativeembodiment, this description is not intended to be construed in alimiting sense. Various modifications of the illustrated embodiment aswell as other embodiments will be apparent to persons of skill in theart. For example, it is possible to modify the system to allow the userto selected the following parameters: (i) total number of 3D image datasets; (ii) time interval of which each individual 3D image data set iscollected; and (iii) aggregate time interval over which all 3D imagedata sets are collected. Further, it is possible, and preferred, todesign the system to allow the use to freeze and, optionally, manipulate(as discussed above) a single frame of the dynamic image display. It istherefore contemplated that the appended claims will cover any suchmodifications or embodiments.

What is claimed is:
 1. A system for the dynamic display ofthree-dimensional (3D) images of a target, comprising: memory means tostore a plurality of time-dependent 3D image data sets; an addresspointer defining an independent address of a location in the memorymeans of each time-dependent 3D image data set; and display meansutilizing the address pointer successively to retrieve a time-dependent3D image data set from memory and display a time-dependent 3D imagecorresponding to the time-dependent 3D image data set for a selectedperiod of time.
 2. A system for the dynamic display of three-dimensional(3D) images of a target volume, the system comprising: scanning means toscan a target volume and generate a succession of digitizedtwo-dimensional (2D) images thereof; timing means to determine the timeinterval between generation of the succession of 2D images;reconstruction means to generate a plurality of time-dependent 3D imagedata sets of the target volume from the succession of digitized 2Dimage; memory means to store the plurality of time-dependent 3D imagedata sets; an address pointer defining an independent address of alocation in the memory means of each time-dependent 3D image data set;and display means utilizing the address pointer successively to retrievea time-dependent 3D image data set from memory and display atime-dependent 3D image corresponding to the time-dependent 3D imagedata set for a selected period of time.
 3. A method for the dynamicdisplay of three-dimensional (3D) images of a target, comprising thesteps: (i) storing a plurality of time-dependent 3D image data sets in amemory; (ii) defining an independent address of a location in the memorymeans for each time-dependent 3D image data set; and (iii) retrieving atime-dependent 3D image data set from memory; (iv) displaying thetime-dependent 3D image corresponding to the time-dependent 3D imagedata set for a selected period of time; and (v) repeating Steps (iii)and (iv) for each remaining time-dependent 3D image data set.
 4. Amethod for the dynamic display of three-dimensional (3D) images of atarget volume, the system comprising: (i) scanning a target volume andgenerating a succession of digitized two-dimensional (2D) imagesthereof; (ii) determining the time interval between generation of thesuccession of 2D images; (ii) generating a plurality of time-dependent3D image data sets of the target volume from the succession of digitized2D image; (iii) storing a plurality of time-dependent 3D image data setsin a memory; (iv) defining an independent address of a location in thememory means for each time-dependent 3D image data set; and (v)retrieving a time-dependent 3D image data set from memory; (vi)displaying the time-dependent 3D image corresponding to thetime-dependent 3D image data set for a selected period of time; and(vii) repeating Steps (v) and (vi) for each remaining time-dependent 3Dimage data set.